My 3D Cursor follows my selection cursor everywhere I click. How do I stop this?
You discovered the Pivot Point

This is a very useful feature in blender 

Your pivot point is for example the rotation axis. 

Maybe you want to rotate something around a Point then select a Vertice/Edge/Face/Object  press  Shift s to position the 3D Cursor.

Now press r and you will rotate aroud the 3D Cursor